Fuligo septica

Fuligo septica is a species of plasmodial slime mold, and a member of the Myxomycetes class. It is commonly known as the dog vomit slime mold[2] or scrambled egg slime because of its peculiar yellowish, bile-colored appearance. A common species with a worldwide distribution, it is often found on bark mulch in urban areas after heavy rain or excessive watering. Their spores are produced on or in aerial sporangia and are spread by wind.

Description and habitat

Like many slime molds, the cells of this species typically aggregate to form a plasmodium, a multinucleate mass of undifferentiated cells that may move in an ameboid-like fashion during the search for nutrients. F. septicas plasmodium may be anywhere from white to yellow-gray,[6] typically 2.5–20 cm (1.0–7.9 in) in diameter, and 1–3 cm (0.4–1.2 in) thick.[7] The plasmodium eventually transforms into a sponge-like aethalium, analogous to the spore-bearing fruiting body of a mushroom; which then degrades, darkening in color, and releases its dark-colored spores. This species is known to have its spores dispersed by beetles (family Lathridiidae).[8]

The spores have a two-layered wall, with a dense outer layer with spines, and a fibrous inner layer. During germination, the outer layer splits to create an opening, and more elastic inner layer ruptures later as protoplasm emerges. A remnant of the inner layer may be persistent and adhere to the protoplast after it has emerged from the spore. A peroxidase enzyme present in the inner cell wall plays a role in germination.[9]

Fuligo septica grows on rotten wood and plant debris, but can also grow on the leaves and stems of living plants.[10]

Close-up of the yellow aethelia

Human pathogenicity

Resistance to metal toxicity

Slime molds have a high resistance to toxic levels of metals; one author was prompted to write "The levels of Zn in Fuligo septica were so high (4,000–20,000 ppm) that it is difficult to understand how a living organism can tolerate them."[13] The resistance to extreme levels of zinc appears to be unique to F. septica.[14] The mechanism of this metal resistance is now understood: F. septica produces a yellow pigment called fuligorubin A, which has been shown to chelate metals and convert them to inactive forms.[15]

Fuligo septica contains a yellow pigment called fuligorubin A that is thought to be involved in photoreception and in the process of energy conversion during its life cycle.[19] In 2011 a Japanese research group reported isolating and characterizing a new chlorine-containing yellow pigment from form flava that they called dehydrofuligoic acid.[20]

^Santili J, Rockwell WJ, Collins RP. (1895). "The significance of the spore of the Basidiomycetes (mushrooms and their allies) in bronchial asthma and allergenic rhinitis". Annals of Allergy55: 469–71.